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International audience; Purpose. Asthma is a frequent chronic inflammatory bronchial disease affecting more than 300 million patients worldwide, 70% of whom are secondary to allergy. The diversity of asthmatic endotypes contributes to their complexity. The inter-relationship between allergen and other exposure and the airway microbiome adds to the phenotypic diversity and defines the natural course of asthma. Here, we compared the mouse models of house dust mite (HDM)-induced allergic asthma. Allergic sensitization was performed via various routes and associated with outcomes.Methods: Mice were sensitized with HDM via the oral, nasal or percutaneous routes. Lung function, barrier integrity, immune response and microbiota composition were analyzed.Results: Severe impairment of respiratory function was observed in the mice sensitized by the nasal and cutaneous paths. It was associated with epithelial dysfunction characterized by an increased permeability secondary to junction protein disruption. Such sensitization paths induced a mixed eosinophilic and neutrophilic inflammatory response with high interleukin (IL)-17 airway secretion. In contrast, orally sensitized mice showed a mild impairment of respiratory function. Epithelial dysfunction was mild with increased mucus production, but preserved epithelial junctions. Regarding lung microbiota, sensitization provoked a significant loss of diversity. At the genus level, Cutibacterium, Acinetobacter, Streptococcus and Lactobacillus were found to be modulated according to the sensitization pathway. An increase in theanti-inflammatory microbiota metabolites was observed in the oral-sensitization group.Conclusions: Our study highlights the strong impact of the sensitization route on the pathophysiology and the critical phenotypic diversity of allergic asthma in a mouse model.

International audience; Background Regulatory T cells (Tregs) are known to protect against allergies. Moreover, the decrease in the frequency and efficiency of Tregs amplifies allergic symptoms. Aim This study investigated whether expanding Tregs in vivo with an IL-2/IL-2 antibody complex could be safe, well tolerated and efficient in a therapeutic setting in allergies. Methods We produced an anti-IL-2 antibody (1C6) and demonstrated that when it is complexed to human IL-2, it increases IL-2 efficiency to induce Tregs in vivo without any detectable side effects. Furthermore, the IL-2/1C6 complex induces an increase in Helios expression by Tregs, suggesting that it not only elevated Treg numbers but also boosted their functions. Using mouse models of house-dust-mite-induced airway inflammation and wheat-gliadin-induced food allergies, we investigated the therapeutic potential of the IL-2/1C6 complex in allergies. Results IL-2/1C6 treatment significantly reduced allergic symptoms, specific IgE production, the adaptive immune response and tissue damage. Interestingly, IL-2/1C6 treatment modulated innate lymphoid cells by increasing ILC2s in asthma and decreasing ILC3s in food allergies. Conclusion In conclusion,complexed IL-2/anti-IL-2 may restore Treg numbers and function in respiratory and food allergies, thereby improving allergic markers and symptoms. Our IL-2/anti-IL-2 complex offers new hope for reestablishing immune tolerance in patients with allergies.

Although there is a growing understanding of immunity against Candida albicans, efforts need to be pursued in order to decipher the cellular mechanisms leading to an uncontrolled immune response that eventually oppose disease eradication. We describe here significant intra- and inter-subject variations in immune response patterns of major human leucocyte subsets following an in vitro challenge with C. albicans clinical isolates. We also observed that there are Candida isolate-dependent changes in leucocyte phenotypes. Through a combination of multiple fungal growth and flow cytometric measurements, coupled to the tSNE algorithm, we showed that significant proliferation differences exist among C. albicans isolates, leading to the calculation of a strain specific persistent index. Despite substantial inter-subject differences in T cells and stability of myeloid cells at baseline, our experimental approach highlights substantial immune cell composition changes and cytokine secretion profiles after C. albicans challenge. The significant secretion of IL-17 by CD66+ cells, IFN-γ and IL-10 by CD4+ T cells 2 days after C. albicans challenge was associated with fungal control. Fungal persistence was associated with delayed secretion of IFN-γ, IL-17, IL-4, TNF-α and IL-10 by myeloid cells and IL-4 and TNF-α secretion by CD4+ and CD8+ T cells. Overall, this experimental and analytical approach is available for the monitoring of such fungal and human immune responses.

Allergic diseases are increasing worldwide, and their precise causes are not fully understood. However, this observation can be correlated with growing chemical pollution of the environment. Bisphenol A (BPA) alters the immune system, microbiota and barrier functions. Here, we studied the effect of oral BPA at levels equivalent to human exposure to understand the mechanisms of immunological, physiological and microbial action on food allergies. In a murine model of allergy, we evaluated the effect of direct oral exposure to BPA at 4 µg/kg bw/d corresponding to tolerable daily intake (TDI). We studied symptoms, intestinal physiology and humorall and cellular immune responses during food allergy. We explored the relationship between oral exposure to BPA and changes in the gut microenvironment. Markers of food allergy and intestinal permeability were increased following exposure to BPA. We also observed a modulated humorall and T-cell response with aggravation of food allergy inflammation. Moreover, BPA exposure induced gut dysbiosis and decreased microbial diversity induced by food allergy. Altogether, these results suggest that the 2015 European Food Safety Authority (EFSA) TDI should be reviewed to consider the immunotoxicity of BPA.

International audience; Sepsis and trauma cause inflammation and elevated susceptibility to hospital-acquired pneumonia. As phagocytosis by macrophages plays a critical role in the control of bacteria, we investigated the phagocytic activity of macrophages after resolution of inflammation. After resolution of primary pneumonia, murine alveolar macrophages (AMs) exhibited poor phagocytic capacity for several weeks. These paralyzed AMs developed from resident AMs that underwent an epigenetic program of tolerogenic training. Such adaptation was not induced by direct encounter of the pathogen but by secondary immunosuppressive signals established locally upon resolution of primary infection. Signal-regulatory protein α (SIRPα) played a critical role in the establishment of the microenvironment that induced tolerogenic training. In humans with systemic inflammation, AMs and also circulating monocytes still displayed alterations consistent with reprogramming six months after resolution of inflammation. Antibody blockade of SIRPα restored phagocytosis in monocytes of critically ill patients in vitro, which suggests a potential strategy to prevent hospital-acquired pneumonia.

Although multiple immune cells participate in the innate and adaptive immune response against Candida albicans, the elucidation of cellular and inflammation kinetics may be a promising strategy to decipher events propitious to infection eradication. We used an in vitro Candida-human leucocyte coculture approach to study the dynamics of rare CD4+CD8+ double positive T lymphocytes (DP T) produced in response to this fungus. Our results highlight the presence of two phenotypically distinct subsets of DP T cells: CD4hiCD8lo and CD4loCD8hi, and that the different ratio of these cells correlates with infection outcome. The ratio of CD4hiCD8lo over CD4loCD8hi by day 6 was significantly higher in controlled infections and decreased when infection persisted due to a significant increase in the proportion of CD4loCD8hi. When infection was controlled, CD4hiCD8lo T cells secreted IFNγ, TNFα, IL-4 and IL-10 cytokines two days after challenge. By day 2, under conditions of persistent infection, CD4hiCD8lo and CD4loCD8hi T cells secreted significant levels of IL-4 and IL-10, respectively, compared to uninfected cultures. Frequency kinetics and original cytokine profiles detailed in this work indicate that DP T cells could participate in the adaptive immune response to C. albicans.

Sepsis and trauma cause inflammation and elevated susceptibility to hospital-acquired pneumonia. As phagocytosis by macrophages plays a critical role in the control of bacteria, we investigated the phagocytic activity of macrophages after resolution of inflammation. After resolution of primary pneumonia, murine alveolar macrophages (AMs) exhibited poor phagocytic capacity for several weeks. These paralyzed AMs developed from resident AMs that underwent an epigenetic program of tolerogenic training. Such adaptation was not induced by direct encounter of the pathogen but by secondary immunosuppressive signals established locally upon resolution of primary infection. Signal-regulatory protein α (SIRPα) played a critical role in the establishment of the microenvironment that induced tolerogenic training. In humans with systemic inflammation, AMs and also circulating monocytes still displayed alterations consistent with reprogramming six months after resolution of inflammation. Antibody blockade of SIRPα restored phagocytosis in monocytes of critically ill patients in vitro, which suggests a potential strategy to prevent hospital-acquired pneumonia.

Objet de l’etude Au cours des candidoses disseminees chroniques (CDC) et des candidoses cutaneo-muqueuses chroniques (CMCD), la reponse physiopathologique se caracterise par une persistance de Candida au sein des granulomes, accompagnee d’une incapacite de l’immunite cellulaire a eradiquer l’infection. Dans ce contexte, la nature precise de l’interaction hote-pathogene reste mal caracterisee. Aussi, le laboratoire EA 1155 IIciMed a recemment mis au point un modele humain in vitro de granulome a C. albicans permettant de decrire la cinetique de formation du granulome suite a l’infection de cellules immunitaires du sang peripherique (PBMC) issues de sujets sains. L’etude actuelle a vise a comparer la reponse granulomateuse pour 8 especes de Candida spp. Methode Notre choix s’est porte sur huit especes de Candida : C. albicans , C. dubliniensis , C. tropicalis , C. lusitaniae , C. glabrata , C. parapsilosis , C. kefyr et C. krusei (4 isolats cliniques par espece). Differents parametres ont ete etudies lors de l’infection de 10 sujets sains immunocompetents : la cinetique de formation, la variation du nombre, de la taille des granulomes, et l’evolution de la charge fongique selon les especes. Resultats Suite a l’infection des PBMC des sujets sains, nous avons observe la formation d’une reponse granulomateuse a partir de j4 puis une augmentation de la moyenne du nombre et de la taille des granulomes entre j4 et j6 post-infection pour le genre Candida . Toutefois, pour le parametre taille, la moyenne est differente selon les especes. Ainsi pour C. albicans et C. dublinensis , la taille moyenne a j6 est de 170 ± 18 microns, et pour les autres especes la taille moyenne est de 63 ± 8 microns. Dans un second temps, les charges fongiques a l’interieur du granulome ont ete calculees et comparees aux donnees de taille montrant a j6 une forte correlation positive ( r = 0,8485). Par ailleurs, alors que la multiplication fongique est controlee a j2 pour toutes les especes, l’evolution des charges fongiques differe ensuite selon l’espece. Deux types de profils se distinguent : le premier se caracterise par une augmentation plus ou moins importante de la levure a partir de j2 tandis que le second se traduit par une clairance progressive du pathogene. Une analyse comparative de ces differentes evolutions prenant en compte egalement les niveaux de charge fongique a j6, a permis de mettre en evidence 4 clusters d’especes. Trois clusters se rattachant au premier profil avec a j6 une charge fongique moyenne elevee (cluster 1 : C. albicans ), moderee (cluster 2 : C. dubliniensis et C. tropicalis ) et faible (cluster 3 : C. lusitaniae , C. glabrata et C. parapsilosis ). Le dernier cluster ( C. krusei et C. kefyr ) correspond au second profil d’evolution des charges. Conclusion Dans nos conditions, l’ensemble des resultats indique que l’interaction entre Candida et les cellules immunitaires de l’hote, passe par la formation de granulomes quel que soit l’isolat clinique en cause. Toutefois, des differences ont ete mises en evidence dans l’evolution de la reponse granulomateuse en termes de taille et de charge fongique en fonction des especes. La presence de filaments ou pseudofilaments au sein du granulome semble avoir un role important lorsque les especes de Candida persistent (clusters 1 et 2). Enfin, l’analyse de ces resultats indique une forte variabilite interindividu dans la reponse granulomateuse dont l’origine est en cours d’etude.